This invention relates to the impingement mixing of two or more fluids. More particularly, this invention relates to an apparatus for mixing and dispensing two or more viscous fluids at high pressure, for producing urethane foam or like material.
Precise mixing of a plurality of fluids, such as the chemicals which make up urethane foam, is highly important to the quality of the product. Proper mixing of these viscous materials under high pressure and temperature controlled conditions is difficult to obtain. In one prior art device, of which we are aware, two fluids are first permitted to comingle in a common chamber. Then the chamber is opened so that the fluids may be dispensed and the mixing thereof is effected by the rotation of a plunger in the chamber. This procedure provides inadequate mixing and dispensing of foam material for a number of reasons. First, when the fluids are permitted to comingle in a common chamber, precise pressure control is necessary to assure that no backflow is created in one line or the other. Further, the mixing which is accomplished by agitation is simply not sufficient to assure a satisfactory product and therefore plunger rotation is required. In addition, no means are provided to recirculate the fluids to maintain them at the precise temperature required to assure a proper chemical reaction upon mixture.
In one device which does provide for recirculation of the fluids when the nozzles are closed, the diversion of the streams of fluid from recirculation to feed is accomplished merely by the opening of the nozzles themselves. This is undesirable primarily because the recirculation must be accomplished at the high pressures necessary to effect the mixing.